The present invention concerns novel macromolecular compounds, their synthesis and their use in mixture with a binder, particularly for paints usable for protecting metal surfaces against corrosion.
Polymers or copolymers bearing phosphonate groups or fluorine groups are already known. Substances of this kind, described more particularly in BE Pat. 09400881, are obtained from a halogenated polymer and/or copolymer activated by at least one peroxide and/or hydroperoxide function, to which at least one phosphonate chain is attached by means of an unsaturated monomer.
The substances described in said patent do protect metal surfaces, but they have many disadvantages.
A first disadvantage of the substances described in the prior art is they must be synthesized from a base material such as a halogenated polymer and/or copolymer of the type of poly(vinylidene fluoride) (PVDF), which is available commercially. Commercial chemicals, however, are highly elaborated and therefore very expensive, thus increasing the cost of the end product.
Another disadvantage is that the polymer and/or copolymer is thermoplastic and therefore sensitive to heat.
A third disadvantage is that activation techniques employing electron beams or ozone are onerous processes.
Yet another disadvantage is that with the materials described in the above-cited document, it is impossible to modulate the protection period of the metal.
In industry, protection for metal parts is desired as a temporary measure, prior to use, or for longer periods of time, depending on the subsequent use of the parts. For instance, it is desirable to be able to store protected parts for periods that can vary by a few months and then be able to use them.
Also known are polymers or copolymers bearing phosphonate groups, film-forming groups and crosslinkable groups.
The state of the art with regard to the synthesis of phosphorus-containing copolymers can be summarized as follows:
phosphate monomers, which are acrylates of the following formula 
described in the patents
U.S. Pat. No. 5,378,291 (Nihon Parkerizing Co.),
PCT WO 88/02 382 (DuPont de Nemours),
EPA 0 221 498 (Johnson et Son),
EPA 0 376 591 (Rohm and Haas),
EPA 0 458 245 A1 (Nippon Paint Co.).
The disadvantages of these materials are, first, their instability with regard to hydrolysis (Cxe2x80x94Oxe2x80x94P bond) and the fact that their double-bond reactivity functionality is higher than 1, which naturally excludes them from the domain of solvated paints.
phosphonated monomers, which are of several types: 
which are described in the patents:
DP 2 232 711 (Stauffer Chem.)
EPA 0 069 31.8 (Hoechst)
Their principal disadvantage, apart from price, is their very poor polymerization reactivity.
styrene monomers: 
which are described in U.S. Pat. No. 3,051,740 (Monsanto).
The disadvantage of these materials is their intricate and costly synthesis.
acrylate monomers 
described in the patents:
EPA 0 278 029 (Dow Chemical)
U.S. Pat. No. 4,658,003 (Dow Chemical),
which may result in chemically unstable end products. In addition, the use and disposal of aldehydes, especially formol, which is a necessity for synthesis, are deprecated for environmental reasons.
fluorophosphonates
CF2xe2x95x90CFxe2x80x94(CF2)xxe2x80x94PO(OH)2
described in the patent EPA 0 398 250 (Daikin).
Their disadvantages are poor radical-polymerization reactivity and very complex preliminary synthesis.
Ordinary paints are composed of a film-forming agent, which forms a film of one or more solvents, pigments and/or colorants on the metal and which hardens at ambient temperature or above. These paints are applied to the metal directly when it is free of oxidation, impurities and/or dirt or after it has undergone an anticorrosion treatment, for example phosphating followed by chromating. The chemicals used for such anticorrosion treatment contain toxic heavy-metal derivatives and highly volatile solvents. Such treatments are therefore harmful both to human health and to the environment.
The following patents can also be cited as belonging to the prior art:
EP 0 516 346, which describes a method for synthesizing certain telomers in an aqueous medium and provides for phosphorus-containing additives.
EP 0 277 711, which cites a few substituent phosphonic groups of polyesters somewhat randomly, without any specific intentions; moreover, it is primarily amines rather than phosphonates that are being sought.
EP 0 035 316, which alludes to mineral zinc phosphate additives rather than organic phosphonates.
The present invention concerns a treatment method and a composition that has the property of ensuring anticorrosion protection and adherence to metal but eliminates the need for prior treatment, particularly the anticorrosion treatments of phosphating and chromating.
To this end, the invention concerns a method for protecting metal articles against corrosion, characterized in that it consists in applying to the metal articles directly, i.e., without prior treatment of any kind, a composition formed, at the least, of a film-forming binder, at least one corrosion-inhibiting additive reactive with metal, and at least one oligomer additive bearing phosphonic acids.
According to other characteristics of this method:
metal articles to be treated whose surfaces are excessively oxidized but not scaled are subjected to coarse brushing to reduce their surface oxidation to a low value that is not necessarily zero, and the composition is then applied to them;
metal articles to be treated whose surfaces are excessively greasy are subjected to coarse cleaning to reduce their surface grease to a low value that is not necessarily zero, and the composition is then applied to them.
The invention also concerns a composition for protecting metal articles against corrosion, comprising a binder and at least one additive, characterized in that it comprises a film-forming binder, at least one corrosion-inhibiting additive reactive with metal, and at least one oligomer additive bearing phosphonic acids.
According to other characteristics of this composition:
it further comprises one or more pigment additives;
it further comprises one or more wetting agents;
the wetting agent includes at least one component selected from the following:
ethoxylated alkyl and aryl phosphonates,
fluorocarbon derivatives,
perfluoroalkylated ammonium sulfonate,
perfluoroalkylated potassium sulfonate,
perfluoroalkylated alcohol amino sulfonate
perfluoroalkylated acrylate
the additives bear a polymer chain compatible with the binder;
the additives are statistical copolymers having blocks or grafts that bear sequences or grafted components compatible with the binder;
the additives are copolymers of at least one monomer compatible with the binder and of at least one phosphonated monomer;
the monomer compatible with the binder is chain-polymerizable and is selected from methacrylic acrylic, styrene, vinyl chloride, vinyl fluoride and vinyl ester monomers;
the monomer compatible with the binder is selected from polycondensable monomers, diols and epoxide diacids;
it includes phosphonic acid groups;
the reactivity additive is a phosphonate or a phosphate whose molecular chains are either hydrocarbonated, fluorinated or chlorofluorinated;
the reactivity additive includes at least one component selected from:
alkyl acid phosphones and phosphonates,
phosphoric acids,
aminotrimethylene phosphonic acid,
1-hydroxyethylidene-1-1-diphosphonic acid,
ethylene diamine tetramethylene phosphonic acid,
hexamethylene diamine tetramethylene phosphonic acid,
diethylene triamine pentamethylene phosphonic acid.
The invention will be better understood from the following detailed description, provided solely as an indicative and nonrestrictive example. The following substances may be cited among those used in the formulations of the inventive composition:
A) Film-forming Binders
These are homopolymers and copolymers obtained from unsaturated monomers used in paints. Said monomers are vinyl, acrylic, styrene, dienic, halogenated or nonhalogenated monomers well known to those skilled in the art.
In the case of reactive binders, the reactivity is most often supplied by carboxylic acid groups, but it can also be supplied by phosphonate groups, which makes the binders more compatible with the additives of the invention.
The phosphonic groups are supplied by monomers that will be described below in connection with the reactive additives.
B) Reactive Additives
These are molecular or macromolecular compounds of low molar mass (less than a few thousand, and preferably close to one thousand).
In addition, these additives all bear phosphorus-containing groups (preferably phosphonic groups), and their primary purpose is to react with metal at its surface. At least one acid function (Pxe2x80x94OH) is therefore necessary.
Three major classes of additives can be contemplated:
Phosphonated alkanes or alkenes
These substances have one or more phosphonic groups at their chain ends and/or within the chain.
The following formulas are possible:
Monophosphonic compounds:
CnH2n+1xe2x80x94Qxe2x80x94PO(OR)2
CnF2n+1xe2x80x94C2H4xe2x80x94Qxe2x80x94PO(OR)2
where Q=nil or SCxH2x and x=2.3
Hxe2x80x94(M)nxe2x80x94PO(OR)2
M=C2F4, C2F3Cl, C3F6, C2F2H2
R=H or alkyl in all cases.
diphosphonic and telechelic compounds
(RO)2OPxe2x80x94Zxe2x80x94PO(OR)2
Zxe2x80x2xe2x80x94N[CH2xe2x80x94PO(OR)2]2
where: R=H, alkyl
Zxe2x80x2 similar to the groups previously described with regard to monophosphonic compounds,
Z=alkylenes or arylenes derived from nonconjugated dienes (divinylbenzene or 1-5-hexadiene, for example)
polyphosphonic compounds:
Structures may contain plural phosphonic groups (xe2x89xa72). For example, with PBHT as the starting material, the following formula is obtained: 
where R=H or alkyl
References:
Polymer Bulletin 41, 145-151 (1998),
Grafting phosphonated thiol on hydroxy telechelic polybutadiene (Bernard Boutevin, Yves Hervaud, Gxc3xa9rard Moutedous) [citation sic].
All-phosphonic statistical telomers and cotelomers
The structures are as follows, respectively:
Rxe2x80x94M1)nxe2x80x94X where nxe2x89xa72
and
Rxe2x80x94(M1)xxe2x80x94(M2)yxe2x80x94X where nxe2x89xa72 (statistical)
The phosphonic groups are supplied either by vinyl, allyl, acrylic or styrene monomers or by telogenic agents (Rxe2x80x94X) of the phosphonate type (alkyl or haloalkyl).
The M2 comonomers are all those generally used in copolymerization, which are well known to those skilled in the art; some examples are: 
where R=H, alkyl from vinyl acetate 
where R=H, alkyl from allyl acetate
Starting with methyl methacrylate (MMA) and phosphonated methyl methacrylate (MAPHOS), radical seeding results, after hydrolysis, in statistical copolymers of the following formula: 
Block phosphonic cotelomers.
Recent advances in controlled radical polymerization have provided access to block copolymers (see xe2x80x9cSynthesis of Block Copolymers by Radical Polymerization and Telomerization,xe2x80x9d Advances in Polymer Science, Vol. 127, pp. 88-112, B. Amxc3xa9duri, B. Boutevin and Ph. Gramain, Ecole Nationale Supxc3xa9rieure de Chimie de Montpellier, URA 1193 CNRS 8, rue Ecole Normale, 34053 Montpellier Cedex France).
In the case of methacrylic derivatives, two methods have been used:
atom-transfer radical polymerization (ATRP).
Example with MMA and MAPHOS: 
from thiuranes, cotelomers similar to the foregoing are obtained as follows: 
(Living radical polymerization of MMA in the presence of piperidinodithiocarbamate derivatives as photoiniferters (cf. Denis Bertin, Bernard Boutevin, Philippe Gramain, Jean-Marc Fabre and Claude Montginoul
Laboratoire de Chimie Appliquxc3xa9e, UPRES A 50760, Ecole Nationale Supxc3xa9rieure de Chimie de Montpellierxe2x80x94Laboratoire de Chimie Structurale Organique, UPRES A 50760, Universitxc3xa9 Montpellier II, Eup. Polym. J. Vol. 34, No. 1, pp. 85-90, 1998, Elsevier Science Ltd.) [citation sic]
C) Anticorrosion Additives
modified zinc, calcium or strontium orthophosphate,
modified zinc or aluminum orthophosphate,
modified organic zinc orthophosphate,
modified zinc or molybdenum orthophosphate,
phosphate, zinc silicate, modified hydrated aluminum,
modified zinc, calcium, aluminum or strontium polyphosphate,
etc.
D) Other Additives
Mineral Pigments:
Aluminum, mica, glass flakes, talc, titanium oxide, iron oxides, barium sulfate, chrome green, graphite, silicas, silicates, etc.
Organic Pigments:
Quinacridones, pyrazolone, isonidoline, quinophthalone, phthalocyanine, indatone, etc.
Surfactants:
ethoxylated alkyl and aryl phosphates,
fluorocarbon derivatives,
perfluoroalkyl ammonium sulfonate,
perfluoroalkyl potassium sulfonate,
perfluoroalkyl aminoalcohol sulfonate,
perfluoroalkyl acrylate.
The invention will be better understood from the following detailed description, provided solely as an indicative and nonrestrictive example.
The invention simplifies the use of paints and coatings and utilizes synergies among the properties of the binders and additives used. In particular, if the binder has good barrier properties and the additive has very good adherence to metal, the resulting materials have excellent corrosion-resistance properties.
Since interpolymer compatibility is a relatively rare characteristic, the polymers that are combined are of the same kind or are very similar, i.e., differing with respect to molecular size or composition, which in most cases is related to the composition of the binder, although they can have some new units.
Phosphonated monomers bear a polymerizable double bond and a phosphonic group, joined to the side chain of the monomer by a Cxe2x80x94P bond. Similarly, polycondensable monomers have a phosphonate group connected to the side chain of the monomer by a Cxe2x80x94P bond.
Examples include styrene monomers of the formula: 
in which R and Rxe2x80x2 are similar or different and equal.
Other examples that can be cited are acrylic monomers of the formula: 
in which R and Rxe2x80x2 are similar or different.
Q=
CH2xe2x80x94CH2 
(CH2)2xe2x80x94Sxe2x80x94(CH2)3
Reaction additives can also be obtained by the chemical modification of commercial oligomers such as PBHT, from Atochem, 
where Z=nil or Sxe2x80x94CH2xe2x80x94CH2.
All the phosphonated additives described above are effective only in acid form.
The chemical transformation of phosphonic esters, whether on monomers or on copolymers, is well known to those skilled in the art and can be performed, in an acidic or basic medium, to obtain phosphonic monoacids, or, using halosilanes, to prepare phosphonic diacids according to the following reaction: 
The following description, provided in regard to nonrestrictively annexed examples, will furnish a better understanding of how the invention can be put to use.